Interpretive Summary: This study compared the comprehension of simple speech syllables in infants and toddlers diagnosed with failure to thrive (FTT) with those of normally growing children. Data were obtained at two ages: 8-18 and 23-27 months. Children heard two speech sounds (pa and ba), with one occurring infrequently and the other infrequently. It was found that the right side of the brain was increasingly involved in the comprehension of language as children age, but less so for FTTs than controls. Two other brain waves were larger to the odd syllable in controls than FTTs (occurring about one-third and the other about two-thirds-three-quarters of a second after the syllable was spoken. These results suggest early differences in the way the brain processes language in the two groups that may relate to the later academic problems of FTT children.

Technical Abstract:
Many studies indicate that normal infants can differentiate speech sounds at birth or in the early days of life, but similar studies have not been done on failure to thrive (FTT) babies. This study investigates syllable discrimination in controls and FTT babies matched for age, race, sex, and SES. The babies (7/group)were studied twice (at ages 8-18 months and ages 23-27 months). Babies heard either /pa/ or /ba/ with one stimulus presented on 20% and the other on 80% of the trials (ISI=2.5 sec, stimulus duration 300 msec, syllables spoken by a male at 72 dB; stimuli alternated across subjects).EEG was recorded from 5 leads (F3, F4, P3, P4, and Cz referenced to the right mastoid).There were two prominent waves, a positive peak occurring at 270 msec and a negative going slow wave between 500-900 ms. Both waves were more prominent in controls than FTTs(p<.001 for each). Difference measures(odd frequent)indicated that controls had a more positive response to odd stimuli between 53 and 235 msec at F3, F4, P3, and Cz on visit1(p<.001 for each site). On visit 2, controls had more positive difference scores to the odd stimulus over the first 500 msec at F3, F4, P4, and Cz(p<.001 for each site). The larger positive right parietal response of controls on visit 2 suggests increasing involvement of the right hemisphere in language processing with increasing age in normal babies (p<.001). On the second visit, the between-group slow wave difference was preserved at Cz,i.e., a more positive difference scores in controls (p<.001). Our previous studies have shown that FTT subjects suffer academic difficulties during the elementary school years. The present findings suggest early differences in language processing that may be related to these later difficulties.